开发常用代码区

1. 查询两个LocalDate类型之间的所有日（周，月）

废弃版本（实际用的时候，发现少了一周）：

long distance = ChronoUnit.WEEKS.between(startDateLocal, endDateLocal);
List<LocalDate> dateList = LongStream.range(0, distance)
        .mapToObj(startDateLocal::plusWeeks)//映射
        .collect(Collectors.toList());//收集

最新版本：

List<LocalDate> dateList = Lists.new ArrayList<>();
long distance = ChronoUnit.WEEKS.between(startDateLocal, endDateLocal);
if (distance >= 1) {
     dateList = Stream.iterate(startDateLocal, d -> d.plusWeeks(1)).limit(distance + 1).collect(Collectors.toList());
}

2. Date类型转LocalDate

LocalDate startDateLocal = startDate.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();

3. 字符串（单个或多个）转List

List<String> list = Arrays.asList("aaa","bbb");

4. 用mysql查询笛卡尔积

select * from
(select a.c1,a.c2,a.c3 from a) e
CROSS JOIN 
(select b.d1,b.d2,b.d3 from b) f

5. mysql使用case…when

select 
case a.a1 when '0' then '就是0' 
else '就是1' end
from a

6. mysql根据查询的数据insert

INSERT INTO table_a(`id`,`name`,`code`) SELECT `id`,`name`,`code` FROM table_b;

INSERT INTO table_a SELECT * FROM table_b;

7. mysql命令行

mysql -uroot -p -h127.00.0.1 -P3306;
show databases;
create database d1;
use d1;

8. mysql修改表字段名/类型/默认值/备注

ALTER TABLE table_a CHANGE name name_code varchar(30) DEFAULT NULL COMMENT '名称';